<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        html,body{
            width: 100%;
            height: 100%;
        }
        .father{
            width: 80%;
            height: 80%;
            margin: 10px;
            border: 1px solid lightblue;
            display: flex;
            flex-wrap: wrap;
            align-content: flex-start;
        }
        .son{
            width: 30%;
            height: 50px;
            background-color: rgb(227, 146, 24);
            border: 1px solid black;
        }
    </style>
    <title>Document</title>
</head>
<body>
    <div class="father">
        <div class="son" style="flex: 6 1 auto;"></div>
        <div class="son" style="flex: 1 2 auto;"></div>
        <div class="son" style="flex: 0 0 auto;"></div>
    </div>
</body>
</html>